Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/50—Amines
  • C08G59/5046—Amines heterocyclic
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/50—Amines
  • C08G59/5093—Complexes of amines

Definitions

• This invention relates to a process for curing polyepoxides. More particularly, this invention relates to a new process for curing polyepoxides, to novel curing agents used in the process, and to useful products obtained from the process.
• This invention further provides cured products obtained by the above process and relates to the novel curing agents described in detail hereinafter.
• Polyepoxides such as, for example, those obtained by reacting epicholorohydrin with polyhydric phenols in the presence of caustic, are promising materials for use in many industrial applications as they can be converted with curing agents to form insoluble, infusible products having good chemical resistance.
• Many conventional polyepoxide-curing agent systems have certain drawbacks that greatly limit the industrial use of the polyepoxides.
• the known mixtures comprising the polyepoxides and aliphatic amines set up rather rapidly. This is true even though the mixtures are stores in airtight containers away from moisture and air. This characteristic necessitates mixing of the components just before use and rapid use of the material before cure sets in. Such a procedure places a considerable burden on the individual operators, and in many cases, gives inferior products because of (1) inefficient mixing, and (2) operations are conducted too rapidly.
• imidazole salts are usually liquids or very low temperature melting solids, whereas normally amine salts are solids with relatively high melting points.
• the imidazole liquid amine salts may be incorporated into the polyepoxide system with ease without considerable stirring and without applying heat to the system.
• these heterocyclic compounds include, among others, the imidazoles, such as substituted imidazoles and benzimidazoles having the structural formulas or mercapto substituted hydrocarbon radicals.
• the acid portion of the salt is selected from an acid, such as phosphoric, acetic, lactic, formic, and the like.
• Especially preferred imidazoles are those wherein the substituent 1s hydrogen or a hydrocarbon radical, and preferably an alkyl, alkenyl, cycloalkyl, cycloalkenyl, aryl, alkaryl or arylalkyl radicals, and particularly those containing no more than 15 carbon atoms and wherein the acid is selected from monocarboxylic acids having from 1 to 8 carbon atoms, lactic, and phosphoric acids.
• imidazole salts include, among others, the acetate, formate, lactate, and phosphate salts of imidazole, benzimidazole, and substituted imidazoles.
• Examples suitable substituted imidazoles include: Z-methylimidazole; 2-ethyl-4-methylimidazole; 2-cyclohexyl-4-methylimidazole; 4-.butyl-5-ethylimidazole; 2-butoxy-4-allylimidazole; 2-carboethoxybutyl 4 methylimidazole, 2-octyl-4- hexyllinmidazole; 2 methyl 5- ethyilimidazole; 2-ethyl-4- phenylimidazole; Z-amide-S-ethylimidazole; 2-ethyl-4-(2- ethylamino)-imidazole; 2-methy1 4 mercaptoethylimidazole; Z-butylacetate-S-methyl-imidazole; 2,5 -chloro-4-ethyllirnidazole; and mixtures thereof.
• alkyl-substituted imidazole acetates and lactates wherein the alkyl groups contain not more than 8 carbon atoms each, or mixtures thereof, and particularly preferred are 2-ethyl-4-methylimidazole acetate, 2-ethyl-4-methylirnidazole lactate, Z-methylimidazole acetate, Z-methylimidazole lactate, imidazole acetate, imidazole lactate, and mixtures thereof.
• the above-described imidazole salts can be prepared by reacting the imidazole with the acid to form the corresponding amine salt.
• the imidazoles are prepared by conventional techniques of reacting a dialdehyde with ammonia and formaldehyde.
• the salts are preferably prepared by mixing the desired acid with the imidazole and maintaining the temperature between 23 and 100 C. Solvents are not necessary but may be employed if desired.
• the reaction is preferably accomplished at temperatures between 23 C. and 150 C. As heat is evolved in the reaction, cooling means may be needed to keep the temperature in the desired range.
• the polyepoxides to be used in preparing the compositions of the present invention comprise those materials possessing more than one vicinal epoxy group, i.e., more than one group. These compounds may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic and may be substituted with substituents, such as chlorine, hydroxyl groups, ether radicals and the like. They may be monomeric or polymeric.
• polyepoxides for clarity, many of the polyepoxides and particularly those of the polymeric type are described in terms of epoxy equivalent values. The meaning of this expression is described in US. 2,633,458.
• the polyepoxides used in the present process are those having an epoxy equivalency greater than 1.0.
• epoxidized esters of the polyethylenically unsaturated monocarboxylic acids such 4 as epoxidized linseed, soybean, perilla, oiticia, tung, walnut and dehydrated castor oil, methyl linoleate, butyl linoleate, ethyl 1,12-octadecadienoate, butyl 9,l2-l5-octadecatrienoate, butyl eleostearate, monoglycerides of tung oil fatty acids, monoglycerides of soybean oil, sunflower, rapeseed, hempseed, sardine, cottonseed oil, and the like.
• epoxy-containing materials used in the process of the invention include the epoxidized esters of unsaturated monohydric alcohols and polycarboxylic acids, such as, for example,
• epoxy-containing materials includes those epoxidized esters of unsaturated alcohols and unsaturated carboxylic acids, such as 2,3-epoxybutyl-3,4-epoxypentanoate,
• Still another group of the epoxy-containing materials included epoxidized derivatives of polyethylenically unsaturated polycarboxylic acids, such as, for example,
• Still another group comprises the epoxidized polyesters obtained by reacting an unsaturated polyhydric alcohol and/or unsaturated polycarboxylic acid or anhydride groups, such as, for example, the polyester obtained by reacting 8,9,12,13-eicosanedienedioic acid with ethylene glycol, the polyester obtained by reacting diethylene glycol with 2-cyclohexene-1,4-dicarboxylic acid and the like, and mixtures thereof.
• an unsaturated polyhydric alcohol and/or unsaturated polycarboxylic acid or anhydride groups such as, for example, the polyester obtained by reacting 8,9,12,13-eicosanedienedioic acid with ethylene glycol, the polyester obtained by reacting diethylene glycol with 2-cyclohexene-1,4-dicarboxylic acid and the like, and mixtures thereof.
• Still another group comprises the epoxidized polyethylenically unsaturated hydrocarbons, such as epoxidized 2,2-bis(2-cyclohexenyl) propane, epoxidized vinyl cyclohexene and epoxidized dimer of cyclopentadiene.
• epoxidized polyethylenically unsaturated hydrocarbons such as epoxidized 2,2-bis(2-cyclohexenyl) propane, epoxidized vinyl cyclohexene and epoxidized dimer of cyclopentadiene.
• Another group comprises the epoxidized polymers and copolymers of diolefins, such as butadiene.
• diolefins such as butadiene.
• examples of this include, among other, butadiene-acrylonitrile copolymers (Hycar rubbers), butadiene-styrene copolymers and the like.
• Another group comprises the glycidyl containing nitrogen compounds, such as diglycidyl aniline and diand triglycidylamine.
• the polyepoxides that are particularly preferred for use in compositions of the invention are the glycidyl ethers and particularly the glycidyl ethers of polyhydric phenols and polyhydric alcohols.
• the glycidyl ethers of polyhydric phenols are obtained by reacting epichlorohydrin" with the desired polyhydric phenols in the presence of alkali.
• Polyether A and Polyether B described in the above-noted U.S. 2,633,458 are good examples of polyepoxides of this type.
• Other examples include the polyglycidyl ether of l,1,2,2-tetrakis(4-hydroxyphenyl) ethane (epoxy value of 0.45 eq./100 g.
• polyglycidyl ether of 1,l,5,5-tetrakis(hydroxyphenyl)pentane epoxy value of 0.514 eq./100 g.
• Other examples include the glycidated novolacs as obtained by reacting epichlorohydrin with novon resins obtained by condensation of aldehyde with polyhydric phenols.
• the heterocyclic curing agent is preferably employed in amounts varying from about 0.1% to about 30% by weight of the polyepoxide, and still more preferably from 1 to by weight of the polyepoxide.
• the heterocyclic curing agent can be used in combination with other components such as phenols, mercaptans, triphenyl phosphorus, triphenyl arsenic, triphenyl antimony, amines, amine salts or quaternary ammonium salts, etc.
• Preferred additives include the mercaptans, phenols, triphenyl phosphorus and the amines, such as, for example, benzyldimethylamine, dicyandiamide, p.p-bis(dimethylaminophenyl)methane, pyridine, dimethylaniline, benzyldimethylamine, dimethylethanolamine, methyldiethanamine, morpholine, dimethylaminopropylamine, dibutylaminopropylamine, stearyldimethylamine, tri-n-butyl amine, triamylamine, tri-n-hexylamine, ethyl din-propylamine, m-phenylenediamine, diethylenetriamine and the like, and mixtures thereof.
• benzyldimethylamine such as, for example, benzyldimethylamine, dicyandiamide, p.p-bis(dimethylaminophenyl)methane
• pyridine
• the salts may be exemplified by the inorganic and organic acid salts of the amines, such as, for example, the hydrochloride, sulfate and acetate of each of the above-described tertiary amines.
• the quaternary ammonium salts may be exemplified by the following: benzyltrimethylammonium chloride, phenyltributylammonium chloride, cyclohexyltributylammonium sulfate, benzyltrimethylammonium sulfate, benzyltrimethylammonium borate, diphenyldioctylammonium chloride, and the like, and mixtures thereof.
• additives include polybasic anhydrides, such as, for example, phthalic anhydride, tetrahydrophthalic anhydride, methyl- 3,6 endomethylene 4 tetrahydrophthalic anhydride, chlorendic anhydride, pyromellitic dianhydride, and the like, and the corresponding acids.
• polybasic anhydrides such as, for example, phthalic anhydride, tetrahydrophthalic anhydride, methyl- 3,6 endomethylene 4 tetrahydrophthalic anhydride, chlorendic anhydride, pyromellitic dianhydride, and the like, and the corresponding acids.
• additives are generally employed in amounts varying from 0.1 part to parts per 100 parts of polyepoxide, and preferably from 1 part to 5 parts per 100 parts of polyepoxide.
• the curing of the polyepoxides may be accomplished by mixing the polyepoxides with the heterocyclic amine salt catalyst and heating the resulting composition at elevated temperatuers, i.e., 150 C.
• the temperatures employed during the cure may vary over a wide range. In general, temperatures ranging from about 60 to 200 C. will give satisfactory results.
• Preferred tempera tures range from about 100 to 175 C. Additional materials, etc., pigment, stabilizers, plasticizers and diluents may be added. One may also add material to accelerate the reaction of the curing agent such as phenols, amines, mercaptans and the like.
• the heterocyclic amine salt catalysts at low levels of concentration impart long term room temperature stabiliy to epoxy resins, e.g., molding materials, without affecting the cure cycle. Because of its stability, the resincatalyst system fl-stages very slowly and remains pliable as it advances in curing allowing time for the material to be molded. The catalysts therefore, are very useful in formulating molding compounds and can be utilized in continuous molding operations.
• compositions of this invention are also useful for preparing laminates.
• the sheets of fibrous material are first treated with the mixture of polyepoxide and curing agent. This is conveniently accomplished by spreading the paste or solution containing the above-noted mixture onto the sheets or glass cloth, paper, textiles, etc.
• the sheets are then superimposed and the assembly cured under heat and pressure.
• the assembly is preferably cured in a heated press under a pressure of about 25 to 500 or more pounds per square inch and temperatures of about 150 C.
• the resulting laminate is extremely strong and resistance against heat and the action of organic and corrosive solvents.
• the fibrous material used in the preparation of the laminates may be of any suitable materials, such as glass cloth and matting, paper, asbestos paper, mica flakes, cotton bats, duck muslin, canvas, synthetic fibers such as nylons, dacron, and the like. It is usually preferred to utilize woven glass cloth that has been given prior treatment with well known finishing or sizing agents, therefore, such as chrome methacrylate or vinyl trichlorosilane.
• compositions of this invention are further useful in filament windings and in casting applications, such as encapsulation and/or embedment of electrical devices and preparation of cast foams containing microballoons.
• EXAMPLE I This example illustrates the preparation of 2-ethyl-4- methylimidazole acetate and its use as a curing agent for Polyether A, i.e., a glycidyl ether of 2,2-bis(4-hydroxyphenyl) propane.
• EXAMPLE II 100 parts of polyether A and 5 parts of 2-ethyl- 4-methylimidazole acetate plus 300 parts of silica filler are thorougly mixed.
• the composition at room temperature has a pot life of 3 weeks. When heated at C., the composition cures to from a hard, insoluble, infusible resin having excellent chemical resistance.
• EXAMPLE III This example illustrates the preparation of imidazole lactate and its use as a curing agent for Polyether A.
• Preparation 68 g. (1 mol) of imidazole is placed in a reaction vessel fitted with a stirrer. 185 g. of 85% lactic acid (1.75 mole) is added to the vessel over a period of 10 minutes while maintaining continuous stirring. The temperature is maintained between 60 C. and 80 C. for 1 hour to complete the reaction.
• the imidazole lactate is lemon colored liquid at room temperature.
• the composition When heated at 150 C., the composition cures to form a resin similar to those of Example I, (a) and (b) having similar properties and gelling times.
• EXAMPLE IV EXAMPLE V Example I is repeated with the exception that Polyether A is replaced by an equivalent amount of a glycidated novalac resin obtained by reacting a phenol-formaldehyde condensate with epichlorohydrin is mixed with 2- ethyl-4-methylimidazole acetate. Similar results are obtained.
• Example I is repeated with the exception that Polyether A is replaced by an equivalent amount of diglycidyl ether of resorcinol and by a 50:50 mixture of Polyether A and epoxidized methyl cyclohexyl methylcyclohexenecarboxylate, respectively. Related results are obtained.
• An acid salt of an imidazole compound selected from the group consisting of 2-butyl-4-allylimidazole acetate, 2- ethyl-4-(2-ethy1amino)imidazole phosphate, 2-amid0-5- ethylirnidazole acetate, 2-methyl-4-mercaptoethylimidazole formate, 2,5-dichloro-4-ethylimidazole lactate and 2- carbo-ethoxybutyl-4-methylimidazole acetate.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Epoxy Resins (AREA)
• Laminated Bodies (AREA)

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Cited By (11)

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Citations (6)

• 0
  • NL NL130329D patent/NL130329C/xx active
• 1965
  • 1965-04-20 DE DES96647A patent/DE1301575B/de not_active Withdrawn
  • 1965-04-20 BE BE662769D patent/BE662769A/xx unknown
  • 1965-04-20 CH CH544065A patent/CH453687A/de unknown
  • 1965-04-20 GB GB16536/65A patent/GB1040039A/en not_active Expired
  • 1965-04-20 SE SE5086/65A patent/SE311752B/xx unknown
  • 1965-04-20 NL NL6504954A patent/NL6504954A/xx unknown
• 1967
  • 1967-07-20 US US664583A patent/US3418333A/en not_active Expired - Lifetime

Patent Citations (6)

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